From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751117AbeDDI7W (ORCPT ); Wed, 4 Apr 2018 04:59:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:34498 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750812AbeDDI7V (ORCPT ); Wed, 4 Apr 2018 04:59:21 -0400 From: Petr Mladek To: Linus Torvalds Cc: Andy Shevchenko , Rasmus Villemoes , "Tobin C . Harding" , Joe Perches , Andrew Morton , Michal Hocko , Sergey Senozhatsky , Steven Rostedt , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH v4 0/9] vsprintf: Prevent silent crashes and consolidate error handling Date: Wed, 4 Apr 2018 10:58:34 +0200 Message-Id: <20180404085843.16050-1-pmladek@suse.com> X-Mailer: git-send-email 2.13.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Crash in vsprintf() might be silent when it happens under logbuf_lock in vprintk_emit(). This patch set prevents most of the crashes by probing the address. The check is done only by %s and some %p* specifiers that need to dereference the address. Only the first byte of the address is checked to keep it simple. It should be enough to catch most problems. The check is explicitly done in each function that does the dereference. It helps to avoid the questionable strchr() of affected specifiers. This change motivated me to do some preparation patches that consolidated the error handling and cleaned the code a bit. Changes against v3: + Add valid_pointer_access() to do the check and store the error message in one call. + Remove strchr(). Instead, validate the address in functions that dereference the address. + Use probe_kernel_address() instead of probe_kernel_real(). + Do the check only for unknown address. + Consolidate handling of unsupported pointer modifiers. Changes against v2: + Fix handling with strchr(string, '\0'). Happens with %p at the very end of the string. + Even more clear commit message + Documentation/core-api/printk-formats.rst update. + Add check into lib/test_printf.c. Changes against v1: + Do not check access for plain %p. + More clear commit message. Petr Mladek (9): vsprintf: Shuffle ptr_to_id() code vsprintf: Consistent %pK handling for kptr_restrict == 0 vsprintf: Do not check address of well-known strings vsprintf: Consolidate handling of unknown pointer specifiers vsprintf: Factor out %p[iI] handler as ip_addr_string() vsprintf: Factor out %pV handler as va_format() vsprintf: Factor out %pO handler as kobject_string() vsprintf: Prevent crash when dereferencing invalid pointers vsprintf: Avoid confusion between invalid address and value Documentation/core-api/printk-formats.rst | 8 + lib/test_printf.c | 37 ++- lib/vsprintf.c | 451 ++++++++++++++++++------------ 3 files changed, 313 insertions(+), 183 deletions(-) -- 2.13.6